November 20, 2001
Question from Aiken, South Carolina, USA:
My daughter, who was diagnosed with type 1 diabetes five months ago, was on Regular and Lente in the morning and Regular and Lente at dinner, but due to high readings in the morning we recently switched the dinner Lente to a third shot at bedtime. Her endocrinologist said that usually a third shot at bedtime is done with NPH, but since she was already on Lente we would try it. I thought that Lente and NPH were basically the same. What is the difference? Can you explain how a peaking insulin can work at night without food after the bedtime snack. Is it metabolized that differently at night?
Lente, which is a 3:7 mixture of Semilente and Ultralente has much the same time frame as NPH. On average, it starts to act a little sooner and lasts a little longer. The differences between the insulins is that in NPH the release in the body is slowed by bonding the insulin to protamine and in the Lente insulins the same effect is achieved by preparing the insulin in a microcrystalline form.
These long acting insulins do indeed peak in the middle of the night and may cause hypoglycemia. The traditional way to avoid this, and still ensure sufficient basal insulin, is to give the evening dose before supper and then to have a high protein bedtime snack both of which can be adjusted for things like vigorous afternoon exercise and appetite changes. If the before-breakfast blood sugars are high this may indeed indicate not enough evening NPH and one logical response, as in this case, would be to give the long-acting insulin at bedtime so that it will still be active in the morning. However, this is not the only interpretation, and a high morning blood sugar may reflect a counterregulatory hormone response to hypoglycemia [the Somogyi Effect] in the very early morning, in which case the evening NPH may actually need to be reduced. The only way to decide which explanation is correct is to do occasional blood sugars in the very early morning to see if they are low or not.
I think you should discuss these possibilities with your daughter’s endocrinologist. I her hemoglobin A1c level is too high, you might also talk about changing to two new insulins, Lantus (insulin glargine) which is usually given separately at bedtime and has an even action over the 24 hours, and Humalog or Novolog which can be given just after the meal so that the dose can be adjusted for appetite and pre meal blood sugar. Some children will dislike this regimen because it does involve four injections including a lunch time one at school.